Israeli warplanes hit a convoy carrying surface-to-surface missiles into Lebanon on Monday night, a senior Israeli security official confirms to TIME. The air strike, around 10:30 p.m. local time on the border between Lebanon and Syria, was the seventh known operation since the Syrian civil war began in 2011 and was an expression of Israel’s only clear policy regarding that deadly conflict: That it will not let Syria’s war become an opportunity for the militant group Hizballah to improve its anti-Israeli arsenal.

The specifics of the missiles targeted by the Monday strike were not immediately available. But the Israeli official indicated they could carry warheads heavier and more dangerous than almost all of the tens of thousands of missiles and rockets Hizballah now has pointed toward Israel. Earlier airstrikes targeted four categories of armaments Israeli officials warned it would destroy if detected moving into Hizballah’s home territory of Lebanon from Syria, where its forces are fighting on behalf of President Bashar Assad:

More accurate surface-to-surface missiles—including the Iranian-made Fateh-110s, targeted in strikes last May 2 and 5 around Damascus. With a range of 190 miles and accurate to within 200 yards, the missiles could threaten specific targets, such as power plants, deep inside Israel.

Long-range precision land-to-sea missiles such as the Russian-made Yakhont hypersonic anti-ship missiles targeted by Israel at least three times last year, in May, July and October. Flying several times faster than sound, the cruise missiles would threaten Israeli ships and off-shore natural gas platforms.

Netanyahu’s remarks followed the fine line Israeli officials typically tread in the wake of such attacks–pointedly tough enough to underscore the country’s “red lines” but stopping short of explicitly acknowledging responsibility, lest leaders of Syria or Hizballah feel obliged to retaliate out of an insult to their pride.

Israeli officials have long said Israel has no clear stake in who prevails in the civil war. A victory for Assad would preserve the devil Israel knows—and by the end of a long war his regime’s military would also be severely degraded, as well as deprived of the chemical arsenal that had been Syria’s primary strategic weapon against Israel. A victory for the opposition might install Sunni extremists, including those linked to al-Qaeda, on its border, next door to the Shia extremists of Hizballah. But that prospect, however unwelcome, has not been enough to bring Israelis to intercede on behalf of Syria and Hizballah, both of whom are backed by archenemy Iran.

“The further we stay away from it, the better it is for Israel,” says retired Israeli diplomat Oded Eran.

And so Israel’s military picks its spots—so far successfully. Analysts say Israeli decision-makers have calculated that Hizballah is too busy in Syria to risk opening a new front with Israel, an estimate that Hizballah appears to share. The airstrikes Monday occurred in darkness—”They still think if they’re driving in convoy at night they can’t be seen,” muses the Israeli security official—in a mountainous area where the border between Syria and Lebanon is poorly marked. But Hizballah’s satellite television news channel Al-Manar reported no strike occurred on the Lebanese side, relieving Hizballah leaders of any reflexive obligation to defend their home turf. The Israeli official said the strike may well have occurred on the Lebanese side of the border, but emphasized that the pilot’s operational decision of where to direct his munitions is driven by a desire to avoid collateral damage—such as nearby civilian houses—”not this side or that side of the border.”

Reports of such air strikes are likely to continue given Hizballah’s determination to gain recompense from the Assad regime that its forces have spilled blood defending, says Eyal Ben-Reuven, a reserve major general who served as deputy head of Israel’s northern command. He spoke Tuesday morning in a conference call arranged by The Israel Project, a non-profit that promotes Israel’s viewpoint to the international press.

“I’m assuming we are not facing any real possibility that Hizballah will attack here on our border,” says Ben-Reuven. “I say that first of all because Hizballah is very busy with fighting in Syria, and with threats inside Lebanon. But that’s our logic,” he adds.

Karl Vick has been TIME's Jerusalem bureau chief since 2010, covering Israel,the Palestine territories and nearby sovereignties. He worked 16 years at the Washington Post in Nairobi, Istanbul, Baghdad, Los Angeles and Rockville, MD.